Light Emitting Diodes (LEDs) are increasingly being adopted as general illumination lighting sources due to their high energy efficiency and long service life relative to traditional sources of light such as incandescent, fluorescent and halogen. Each generation of LEDs are providing improvements in energy efficiency and cost per lumen, thus allowing for lighting manufacturers to produce LED light fixtures at increasingly cost competitive prices. These reduced costs are expanding the applications of LED lighting from niche markets, such as outdoor street lighting, Christmas lights and flashlights, to general illumination within offices, retail, industrial, and residential environments.
LEDs that are utilized in general illumination applications typically are white LEDs composed of blue LEDs with a yellow phosphor coating. These white LEDs appear white to the human eye and can be manufactured at various color temperatures. Although these white LEDs can provide sufficiently high quality “white” light for many applications, they do not provide a full spectrum of light similar to sunlight.
To address this, in some implementations, LED light fixtures are utilizing RGB (red, blue, green) or RGBA (red, blue, green, amber) LED modules that allow for a mixture of limited spectrum LEDs focused on particular color spectrums to be mixed to create white light. The use of RGB and RGBA LED modules allows control over the color of the LED fixture and can enable an improved full spectrum “white” light to be projected when the correct balance of red, blue, green and amber LEDs are utilized. In some cases, both white LEDs and RGB/RGBA LED modules are utilized in the same fixture. The mixing of the light spectrum from the white LEDs and the RGB/RBGA modules can increase the CRI (Color Rending Index) for the fixture relative to a fixture only using standard white LEDs. This increase in CRI can also occur if the fixture simply includes white LEDs with some red and/or green LEDs properly balanced.
Despite the addition of different spectrums mixed together, light fixtures using RGB/RGBA modules do not replicate natural sunlight particularly well. On a sunny day, sunlight in its purest form is made up of many different spectrums of light coming from many different directions. It may include direct light from the sun that may have a very complete spectrum, indirect light from diffuse sky radiation and reflections of both of these lights from the Earth and terrestrial objects.
There is a push within building designs to incorporate more natural daylighting in work spaces through the use of more windows and the addition of sky lights. Unfortunately, using natural light to illuminate spaces is not always practical and artificial lighting is required. Against this background, there is a need for solutions that will mitigate at least one of the above problems, particularly improving the light output from LED lighting apparatus to better replicate sunlight.
It is to be expressly understood that the description and drawings are only for the purpose of illustration of certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention.